PROJECT SUMMARY OF THE ANALYTICAL CORE (CORE 2) Characterization of natural product (NP) study materials with respect to the chemistry of their phytoconstituents is fundamental to the mechanistic elucidation of pharmacokinetic natural product-drug interactions (NPDIs). Unlike drug products, NPs are inherently complex mixtures that vary substantively in bioactive constituent composition, both between brands and between batches of the same brand. The Analytical Core will develop a comprehensive strategy to overcome these challenges, building upon a unique and longstanding collaboration between the Analytical Core Leader Dr. Oberlies (a NP chemist) and the Co-PI Dr. Paine (a clinical pharmacologist). The responsibilities of the Analytical Core are to 1) characterize the chemistry components of the 4-6 NPs selected for the Interaction Projects; 2) source, acquire, and analyze the selected NPs obtained from commercial vendors to assure adequate and quality supply of study materials for the Interaction Projects; and 3) conduct bioanalysis of NP constituents, drugs, and their relevant metabolites in pharmacokinetic samples collected from the Interaction Projects. The first responsibility will include an in- depth literature evaluation, acquiring or isolating de novo the reference standards (depending on commercial availability), and structurally characterizing the constituents with a suite of spectroscopy and spectrometry tools. When appropriate, key known in vivo metabolites of the NP constituents (e.g., glucuronides) will be generated. The reference standards, both individually or as admixtures, will be used for in vitro studies to generate interaction matrices and will serve as calibration standards for later bioanalysis of NP constituents in the pharmacokinetic samples. The second responsibility will include establishing specifications for each study NP based on the characterization data and identifying a suitable commercial manufacturer/vendor who can supply the required amount of study material meeting the established criteria. Quality of the study materials will be assured by analyzing of the dosage units for 1) content uniformity of the key constituents, 2) stability of the key constituents, 3) contaminants, and 4) dosage performance as assessed by dissolution testing. Commercial products that satisfy strict quality assurance and quality controls will be advanced to the Interaction Projects. The third responsibility will include quantifying NP constituent, victim drug, and relevant metabolite concentrations in pharmacokinetic samples obtained from subjects participating in the Interaction Projects. Dr. Shen and Dr. Paine have extensive experience in the bioanalysis of drugs and metabolites in biofluids for pharmacokinetic profiling; their laboratories at UW and WSU, respectively, offer a complementary portfolio of assays, including NP constituents and phenotyping probe drugs, using state-of-the-art LC-MS/MS instrumentation. The collective NP chemistry and bioanalytical expertise of the Analytical Core investigators ensures accomplishment of the milestones set forth for this Core, thereby helping to advance the understanding of NPDIs and their clinical relevance.